The present invention relates to an image processing method and apparatus which allows the recording of three dimensional topographical information onto a two dimensional medium, for example by processing the data such as to enable the subsequent display of such information on a visual display unit (VDU).
Conventionally three-dimensional topographical information may be processed to allow it to be recorded on a two-dimensional medium such as a visual display unit by the allocation of different colours to represent height information data values along an axis extending normally to the two-dimensional surface. The colours may comprise different shades of grey.
However, such a method takes no account of factors other than basic height information.
An image processing apparatus for providing image data for forming an image on an image carrier, which image is representative of a characteristic of a surface. The apparatus has input means for inputting a plurality of height values, each height value being representative of the height at a respective different point on the surface. Processing means is provided for calculating gradient data at a plurality of different points on the surface from the input height values. The gradient data is adjusted dependent upon a selected angle of illumination. Image data is generated by combining the corresponding values of the adjusted gradient data and the input height value for a plurality of different points. The processing means is arranged to combine the corresponding values of the adjusted gradient data and the input height value to generate the image data according to the relationship:
Image_Data (x,y)=S*Height (x,y)+T*Gradient (x,y);
where Image_Data (x,y), Height (x,y) and Gradient (x,y) are the values of the image data, the input height and the adjusted gradient data at a point (x,y) on the surface respectively and S and T are weighting coefficients. An output means is provided for outputting said image data.
An embodiment of the present invention concerns the provision of an image processing method and apparatus which perform a low amount of data processing yet can produce data suitable for recording which account for both height, local gradient and angle of illumination information thereby providing an improved indicator of topology.
One application of the present invention is to provide apparatus suitable for processing the data produced by metrological instruments used to determine surface roughness or texture. Yet more particularly an embodiment of the invention is suitable for use for display processing in the metrological instrument described in United Kingdom published patent application GB-A-2287790, in the name of the applicant hereof. That instrument is of the type in which a stylus is driven across the surface to be measured so as to detect very small surface features to provide a measure of surface roughness or texture. Such apparatus is typically used for quality control, fault detection and the like.